1. Field of the Invention
The present invention relates to the field of gravity-powered toilets for removal of human and other waste. The present invention further relates to the field of toilets that can be operated at reduced water volumes.
2. Description of Related Art
Toilets for removing waste products, such as human waste, are well known. Gravity powered toilets generally have two main parts: a tank and a bowl. The tank and bowl can be separate pieces which are coupled together to form the toilet system (commonly referred to as a two-piece toilet) or can be combined into one integral unit (typically referred to as a one-piece toilet).
The tank, which is usually positioned over the back of the bowl, contains water that is used for initiating flushing of waste from the bowl to the sewage line, as well as refilling the bowl with fresh water. When a user desires to flush the toilet, he pushes down on a flush lever on the outside of the tank, which is connected on the inside of the tank to a movable chain or lever. When the flush lever is depressed, it moves a chain or lever on the inside of the tank which acts to lift and open the flush valve, causing water to flow from the tank and into the bowl, thus initiating the toilet flush.
There are three general purposes that must be served in a flush cycle. The first is the removal of solid and other waste to the drain line. The second is cleansing of the bowl to remove any solid or liquid waste which was deposited or adhered to the surfaces of the bowl, and the third is exchanging the pre-flush water volume in the bowl so that relatively clean water remains in the bowl between uses. The second requirement, cleansing of the bowl, is usually achieved by way of a hollow rim that extends around the upper perimeter of the toilet bowl. Some or all of the flush water is directed through this rim channel and flows through openings positioned therein to disperse water over the entire surface of the bowl and accomplish the required cleansing.
Gravity powered toilets can be classified in two general categories: wash down and siphonic. In a wash-down toilet, the water level within the bowl of the toilet remains relatively constant at all times. When a flush cycle is initiated, water flows from the tank and spills into the bowl. This causes a rapid rise in water level and the excess water spills over the weir of the trapway, carrying liquid and solid waste along with it. At the conclusion of the flush cycle, the water level in the bowl naturally returns to the equilibrium level determined by the height of the weir.
In a siphonic toilet, the trapway and other hydraulic channels are designed such that a siphon is initiated in the trapway upon addition of water to the bowl. The siphon tube itself is an upside down U-shaped tube that draws water from the toilet bowl to the wastewater line. When the flush cycle is initiated, water flows into the bowl and spills over the weir in the trapway faster than it can exit the outlet to the sewer line. Sufficient air is eventually removed from the down leg of the trapway to initiate a siphon which in turn pulls the remaining water out of the bowl. The water level in the bowl when the siphon breaks is consequently well below the level of the weir, and a separate mechanism needs to be provided to refill the bowl of the toilet at the end of a siphonic flush cycle to reestablish the original water level and protective “seal” against back flow of sewer gas.
Siphonic and wash-down toilets have inherent advantages and disadvantages. Siphonic toilets, due to the requirement that most of the air be removed from the down leg of the trapway in order to initiate a siphon, tend to have smaller trapways which can result in clogging. Wash-down toilets can function with large trapways but generally require a smaller amount of pre-flush water in the bowl to achieve the 100:1 dilution level required by plumbing codes in most countries (i.e., 99% of the pre-flush water volume in the bowl must be removed from the bowl and replaced with fresh water during the flush cycle). This small pre-flush volume manifests itself as a small “water spot.” The water spot, or surface area of the pre-flush water in the bowl, plays an important role in maintaining the cleanliness of a toilet. A large water spot increases the probability that waste matter will contact water before contacting the ceramic surface of the toilet. This reduces adhesion of waste matter to the ceramic surface making it easier for the toilet to clean itself via the flush cycle. Wash-down toilets with their small water spots therefore frequently require manual cleaning of the bowl after use.
Siphonic toilets have the advantage of being able to function with a greater pre-flush water volume in the bowl and greater water spot. This is possible because the siphon action pulls the majority of the pre-flush water volume from the bowl at the end of the flush cycle. As the tank refills, a portion of the refill water is directed into the bowl to return the pre-flush water volume to its original level. In this manner, the 100:1 dilution level required by many plumbing codes is achieved even though the starting volume of water in the bowl is significantly higher relative to the flush water exited from the tank. In the North American markets, siphonic toilets have gained widespread acceptance and are now viewed as the standard, accepted form of toilet. In European markets, wash-down toilets are still more accepted and popular. Whereas both versions are common in the Asian markets.
Gravity powered siphonic toilets can be further classified into three general categories depending on the design of the hydraulic channels used to achieve the flushing action. These categories are: non-jetted, rim jetted, and direct jetted.
In non-jetted bowls, all of the flush water exits the tank into a bowl inlet area and flows through a primary manifold into the rim channel. The water is dispersed around the perimeter of the bowl via a series of holes positioned underneath the rim. Some of the holes are designed to be larger in size to allow greater flow of water into the bowl. A relatively high flow rate is needed to spill water over the weir of the trapway rapidly enough to displace sufficient air in the down leg and initiate a siphon. Non-jetted bowls typically have adequate to good performance with respect to cleansing of the bowl and exchange of the pre-flush water, but are relatively poor in performance in terms of bulk removal. The feed of water to the trapway is inefficient and turbulent, which makes it more difficult to sufficiently fill the down leg of the trapway and initiate a strong siphon. Consequently, the trapway of a non-jetted toilet is typically smaller in diameter and contains bends and constrictions designed to impede flow of water. Without the smaller size, bends, and constrictions, a strong siphon would not be achieved. Unfortunately, the smaller size, bends, and constrictions result in poor performance in terms of bulk waste removal and frequent clogging, conditions that are extremely dissatisfying to end users.
Designers and engineers of toilets have improved the bulk waste removal of siphonic toilets by incorporating “siphon jets.” In a rim-jetted toilet bowl, the flush water exits the tank, flows through the manifold inlet area and through the primary manifold into the rim channel. A portion of the water is dispersed around the perimeter of the bowl via a series of holes positioned underneath the rim. The remaining portion of water flows through a jet channel positioned at the front of the rim. This jet channel connects the rim channel to a jet opening positioned in the sump of the bowl. The jet opening is sized and positioned to send a powerful stream of water directly at the opening of the trapway. When water flows through the jet opening, it serves to fill the trapway more efficiently and rapidly than can be achieved in a non-jetted bowl. This more energetic and rapid flow of water to the trapway enables toilets to be designed with larger trapway diameters and fewer bends and constrictions, which, in turn, improves the performance in bulk waste removal relative to non-jetted bowls. Although a smaller volume of water flows out of the rim of a rim jetted toilet, the bowl cleansing function is generally acceptable as the water that flows through the rim channel is pressurized. This allows the water to exit the rim holes with higher energy and do a more effective job of cleansing the bowl.
Although rim-jetted bowls are generally superior to non-jetted, the long pathway that the water must travel through the rim to the jet opening dissipates and wastes much of the available energy. Direct-jetted bowls improve on this concept and can deliver even greater performance in terms of bulk removal of waste. In a direct-jetted bowl, the flush water exits the tank and flows through the bowl inlet and through the primary manifold. At this point, the water is divided into two portions: a portion that flows through a rim inlet port to the rim channel with the primary purpose of achieving the desired bowl cleansing, and a portion that flows through a jet inlet port to a “direct-jet channel” that connects the primary manifold to a jet opening in the sump of the toilet bowl. The direct jet channel can take different forms, sometimes being unidirectional around one side of the toilet, or being “dual fed,” wherein symmetrical channels travel down both sides connecting the manifold to the jet opening. As with the rim jetted bowls, the jet opening is sized and positioned to send a powerful stream of water directly at the opening of the trapway. When water flows through the jet opening, it serves to fill the trapway more efficiently and rapidly than can be achieved in a non-jetted or rim jetted bowl. This more energetic and rapid flow of water to the trapway enables toilets to be designed with even larger trapway diameters and minimal bends and constrictions, which, in turn, improves the performance in bulk waste removal relative to non-jetted and rim jetted bowls.
Several inventions have been aimed at improving the performance of siphonic toilets through optimization of the direct jetted concept. For example, in U.S. Pat. No. 5,918,325, performance of a siphonic toilet is improved by improving the shape of the trapway. In U.S. Pat. No. 6,715,162, performance is improved by the use of a flush valve with a radius incorporated into the inlet and asymmetrical flow of the water into the bowl.
Although direct fed jet bowls currently represent the state of the art for bulk removal of waste, there are still major needs for improvement. Government agencies have continually demanded that municipal water users reduce the amount of water they use. Much of the focus in recent years has been to reduce the water demand required by toilet flushing operations. In order to illustrate this point, the amount of water used in a toilet for each flush has gradually been reduced by governmental agencies from 7 gallons/flush (prior to the 1950's), to 5.5 gallons/flush (by the end of the 1960's), to 3.5 gallons/flush (in the 1980's). The National Energy Policy Act of 1995 now mandates that toilets sold in the United States can use water in an amount of only 1.6 gallons/flush (6 liters/flush). Regulations have recently been passed in the State of California which require water usage to be lowered ever further to 1.28 gallons/flush. The 1.6 gallons/flush toilets currently described in the patent literature and available commercially lose the ability to consistently siphon when pushed to these lower levels of water consumption. Thus, manufacturers will be forced to reduce trapway diameters and sacrifice performance unless improved technology and toilet designs are developed.
A second, related area that needs to be addressed is the development of siphonic toilets capable of operating with dual flush cycles. “Dual flush” toilets are designed to save water through incorporation of mechanisms that enable different water usages to be chosen depending on the waste that needs to be removed. For example, a 1.6 gallon per flush cycle could be used to remove solid waste and a 1.2 gallon or below cycle used for liquid waste. Prior art toilets generally have difficulty siphoning on 1.2 gallons or lower. Thus, designers and engineers reduce the trapway size to overcome this issue, sacrificing performance at the 1.6 gallon cycle needed for solid waste removal.
A third area that needs to be improved is the bowl cleansing ability of direct jetted toilets. Due to the hydraulic design of direct jetted bowls, the water that enters the rim channel is not pressurized. Rather, it spills into the rim channel only after the jet channel is filled and pressurized. The result is that the water exiting the rim has very low energy and the bowl cleansing function of direct jet toilets is generally inferior to rim jetted and non-jetted.
Therefore, there is a need in the art for a toilet which overcomes the above noted deficiencies in prior art toilets, which is not only resistant to clogging, but allows for sufficient cleansing during flushing, while allowing for compliance with water conservation standards and government guidelines.